The present invention pertains to a device for transporting material strips made of rubber or a rubber-like synthetic material and for depositing such material strips on an installation drum for pneumatic tires or its parts, in particular, for depositing narrow apex strips on a bellows drum, wherein the advancing material strips are cut to length from an endless material and are positioned on a pattern table within the region of the device. The device contains pivotable receptacle devices that can be displaced in the transport direction and that are used to take hold of at least one end of the material strips positioned on the pattern table in order to transport the material strips to the depositing position and to deposit said material strips on the installation drum.
When manufacturing a new tire, the internal ply of a tire is deposited first on a tire installation drum, and then a carcass layer is deposited on the inner ply. The bead cores, including the apex, are then attached while the installation drum is expanded. The bead core and the apex form a pre-fabricated unit that is manufactured on a separate drum (bellows drum) and laterally pushed and positioned on the layers already located on the tire installation drum in the form of pre-fabricated rings. During the pre-fabrication, the apex profiles/bead filler profiles, which have the shape of material strips, are fixed to the bellows drum with one end either manually or with the aid of small vacuum suction cups and then rolled thereon.
The next process taking place on the tire installation drum is the high-impact process, in which the carcass layer ends are folded around the bead cores. This process is carried out with the aid of bellows. Subsequently, another carcass layerxe2x80x94if such a second layer is providedxe2x80x94as well as the side strips (side wall parts) and the horn profiles are attached. The tire carcass is now finished and can be removed from the installation drum, which is returned to its original position.
The additional installation begins with the transfer of the tire carcass to a second installation machine with another installation drum that contains a cambering part. The belt layers that usually consist of two or three rubberized steel cord layers are deposited on a separate belt drum and, if required, provided with one or two layers of a nylon bandage. Belt buffer strips may be arranged between the individual belt layers. If required, the cover strip is provided with a lower plate that is finally deposited on this belt packet. A transfer device that contains a carrying ring for the belt/cover strip packet transports the belt/cover strip packet to the tire carcass and positions it over said carcass. The tire carcass which is already centered and pre-cambered is now completely cambered and joined with the belt/cover strip packet, with the cover strip including the belt packet being rolled on after removing the transfer device.
The described method is a so-called two-stage installation. However, conventional one-stage methods are also used. In this case, the manufacturing of the carcass and the finishing of the base tire takes place within a single tire assembly system with several assigned drums.
The finished base tire is vulcanized in a corresponding vulcanization mold that provides the tire with its final shape, with an integrated cover strip profile and side walls that contain lettering or decorative designs.
Known manufacturing methods are composed of individual steps with precisely defined production sequences, all of which contribute to determining the quality and the properties of the finished product. Among other things, special care is required during the manufacturing of the apex or core filler profiles that are processed further in the form of a unit together with the bead cores and that usually have the shape of material strips with a more or less triangular cross section. The material strips are deposited on the bellows drum with one of the longer sides of the triangle, rolled on and connected to one another within the end regions.
The depositing of the apex profiles is associated with certain difficulties due to the fact that the profile strips, which essentially have a triangular cross section, are extremely sensitive to mechanical stresses, cuts, expansions and bending. In addition, different stability properties and elasticities of the material caused by the geometry exist in the plastic state due to the cross section that is tapered over the width of the strip, and it is extremely difficult to deposit the edges in an exactly linear fashion without waves and bends.
The handling of such apex strips also becomes more difficult due to the fact that the surfaces of such profiles, which are beveled on one side, make it very difficult to adapt the holding and transport elements, e.g., suction cups. Consequently, a manual deposition or a manual correction is required in many instances.
In addition to the macrogeometric design in the form of a bevel, texture characteristics of the surface frequently are the source of problems in handling the strips. If certain time periods between the emergence from the extruder and the deposition on the drum are exceeded or, for example, recycling material is incorporated into such strips, an uneven surface with many small waves, ripples or elevations will often be formed. This means that vacuum suction cups can no longer be used and a manual deposition needs to be carried out.
Another problem in handling apex strips is caused by the trend to use narrow apex profiles, e.g., apex profiles required for low-profile tires or special constructions. Generally, apex strips, in which the long sides of the triangle have a width of approximately 60 mm, have been used up until now. Today, apex strips, in which the corresponding width is merely 10-15 mm, are frequently manufactured.
The handling of such narrow apex strips is also limited with respect to miniaturizing the holding elements for automatic deposition devices. For example, the application limit with respect to the conventionally used suction cups is already reached at an apex strip width of 15 mm, and a secure retention and handling can no longer be ensured. Consequently, one is forced to resort to a manual deposition method that interrupts with and disadvantageously influences the entire manufacturing process.
U.S. Pat. No. 3,904,471 (Kubinsky et al.) shows a tire installation device for depositing a narrow material strip which consists of a depositing wheel that is equipped with needles on its outer side and that engages or is in tangential rolling contact with the tire installation drum. The tire installation drum and the needle wheel are pressed against one another under pressure and roll on one another such that the narrow strip to be deposited is pressed onto the tire installation drum. After one complete circumferential revolution, the strip is cut to length with a hot knife in the vicinity of the needle wheel and the resulting part is then pressed onto the drum.
The disadvantages of this device are the high pressure, with which the needle wheel is pressed against the tire installation drum that is provided with a flexible casing for expansion purposes, and the resulting extreme wear of the drum surface. In addition, it is difficult to realize the movement of the needle wheel relative to the movement of the installation drum while these two components roll in contact with one another and while pulling the needles out of the deposited material. The resulting direction of movement of a needle tip after it passes the contact point between the drum and the needle wheel is oriented tangential to the outer circumference of the needle wheel, and the deposited material follows the contour of the installation drum. Consequently, a xe2x80x9ctear-off movementxe2x80x9d results due to the radial component of movement of the needle tip. This results in the adhesion of the material strip on the installation drum caused by the partial elimination of the contact pressure, and also relatively long tear-out traces that remain in the material.
If material strips are intended to be deposited with reinforcing elements by means of such a device, a few of the reinforcing elements may be pulled out while the drum and the wheel roll in contact with one another.
It is therefore an object of the invention to provide a transport and deposition device for depositing material strips made of rubber or a rubber-like synthetic material on an installation drum. More particularly, it is an object of the present invention to be able to deposit narrow apex strips of any geometric configuration and an arbitrarily designed surface automatically and without any handling problems. A further object of the present invention is that the device should have a simple and practical design and should be easily incorporated into existing manufacturing systems.
The above and other objects of the present invention can be achieved by a device as described below. The device of the present invention is for transporting material strips made of rubber or a rubber-like synthetic material and for depositing such material strips on an installation drum for pneumatic tires or its parts, and in particular, for depositing narrow apex strips on a bellows drum. There, the advancing material strips are cut the length from an endless material and positioned on a pattern table within the region of the device. A feature of the device of the invention is the presence of pivotable receptacle devices that can be displaced in the transport direction and which can be displaced in the transport direction and which can take hold of at least one end of the material strips positioned on the pattern table in order to transport the material strips to the depositing position and to deposit these material strips on the installation drum. The receptacle devices can be displaced in a transport direction that is essentially tangential to the surface or circumference of the installation drum and the receptacle devices contain one or more holding elements that penetrate into the material strip and produce a temporary and detachable positive connection with the material strip.
Due to this design of the device, a precise retention and fixing of the material strips to be deposited is achieved that does not depend on the surface structure or the profile geometry. In addition, the essentially tangential transport direction, which makes it possible to transfer the material without sudden changes in the drum movement, provides a continuous and interference-free deposition on the installation drum or on the bellows drum without damage to the material.